Photonics generates terahertz through terahertz photoconductive antenna, optical rectification and nonlinear difference frequency. The principle of terahertz generation in photonics is to excite some narrow-band gap semiconductors with laser pulses. Due to the vertical asymmetry of the excited carrier distribution, it will cause macroscopic charge movement, thus exciting terahertz radiation. Terahertz science and technology is a new science and technology developed in recent ten or twenty years, which has great application value in object imaging, medical diagnosis, broadband and satellite communication. However, the generation and detection technology of terahertz wave is not mature, which greatly restricts its development.

Introduction to terahertz

Semiconductor terahertz radiation source, the principle of semiconductor terahertz radiation can be summarized into two aspects, namely photoinduced multiplication effect and surface electric field effect. Photomultiplication effect is to excite some semiconductors with narrow band gaps by laser pulses, which shows that the vertical asymmetry of excited carrier distribution will cause macroscopic charge movement, thus exciting terahertz radiation.

The surface electric field effect is that for some semiconductors with wide band gaps, there are surface states on their surfaces. Due to the inconsistency between the surface and the internal Fermi level, the surface electric field will be generated. Due to the existence of this electric field, the carriers excited by laser will generate transient current, thus forming terahertz radiation.